Question: $\left(10x - 7\right)\left(-8x + 9\right) = \ ?$
Solution: $= 10x \cdot \left(-8x + 9\right) - 7 \cdot \left(-8x + 9\right)$ $= \left( 10x \cdot -8x \right) + \left( 10x \cdot 9 \right) + \left( -7 \cdot -8x \right) + \left( -7 \cdot 9 \right)$ $= -80x^2 + \left( 10x \cdot 9 \right) + \left( -7 \cdot -8x \right) + \left( -7 \cdot 9 \right)$ $= -80x^2 + \left( 90x + 56x \right) + \left( -7 \cdot 9 \right)$ $= -80x^2 + 146x + \left( -7 \cdot 9 \right)$ $= -80x^2 + 146x - 63$